The optical spectrum of the strained double perovskite SCIO was obtained within the I.P. approximation. Additionally, quasiparticle effects were considered with a single shot \(G_{0}W_{0}\)  calculation[1]} and excitonic effects by solving the BSE[2]}, [3]}. For the calculation of the real and imaginary part of the dielectric function we used 50 frequency grid points with a cut-off energy of 600 eV. A total of 48 valence and 54 conduction bands were employed for the calculation of the BSE spectrum, which ensures convergence of the spectrum up to at least 3 eV. A Gaussian broadening of 0.1 eV is used for the I.P. and \(G_{0}W_{0}\)  spectrum and 0.05 eV for the BSE spectrum.
